KR100491934B1 - Particle tolerant printhead - Google Patents

Abstract

An island 301 of material of the barrier layer 213 of the inkjet printhead is disposed between the ink supply and the ink supply channel leading to the ink firing chamber to filter particulates in the ink. The dimensions of the ink supply channel and ink ejection orifice are reduced in size, and the thickness of the barrier layer is made thinner. The nominal size of the filter pores is smaller than the barrier layer thickness, while the width of the ink supply channel and the aperture of the orifice are greater than the barrier layer thickness.

Description

Particle-tolerant printheads and manufacturing method thereof {PARTICLE TOLERANT PRINTHEAD}

BACKGROUND OF THE INVENTION Field of the Invention The present invention relates generally to printheads for inkjet printers, in particular by applying a particle tolerant ink feed filter of small dimensions to reduce particulate blockage while maintaining high ink fill rates. Pertaining to a printhead.

Inkjet printers operate by ejecting a small amount of ink through a plurality of small orifices on a surface held in close proximity to the media on which marks or printing are to be placed. These orifices are arranged in a predetermined form within the surface to eject ink drops from a selected number of orifices for a particular location of the media to form part of the desired character or image. Ejecting other ink droplets after controlled repositioning of the orifice support surface or media creates more segments of the desired text or image. In addition, various colors of ink are coupled to each orifice arrangement such that selected firing of the orifices can form a multicolor image by an inkjet printer.

Several instruments, such as thermal instruments, piezoelectric instruments, and electrostatic instruments, have been used to generate the force required to eject ink droplets from the printhead. Although the following description is made with reference to a thermal ink ejection mechanism, the present invention can also be applied to other ink ejection mechanisms.

Ink droplet ejection in a conventional thermal inkjet printer is achieved by rapidly heating the ink to a temperature above the boiling point of the ink solvent to produce vapor phase ink bubbles. In general, rapid heating of the ink is achieved by passing a pulse of current through the ink ejector, which is an addressable heater resistor, typically for 1 microsecond to 3 microseconds, and so occurs. The heat is transferred to a small amount of ink that is maintained in a closed area, commonly referred to as a firing chamber. One of the hermetic walls of the firing chamber is formed by a surface pierced by a plurality of orifices. One of the orifices in this orifice plate is arranged relative to the heater resistor so that ink can be ejected from the orifice. When ink vapor bubbles are generated and expand in the heater resistor, a predetermined amount of ink is moved to cause the same amount of ink to exit the orifice and adhere on the medium. The bubble then collapses and the discharged amount of ink is replenished from the large ink reservoir through an ink supply channel in one of the walls of the firing chamber.

It is desirable to refill the ink as quickly as possible, thereby allowing a very rapid launch of the orifice of the printhead. Rapid launch of the orifice results in the ability to achieve high speed printing of the inkjet printer. Prior to the next firing of the heater resistor, the ink must have enough time to replenish the chamber so that no undesirable changes in the size of the ink drop occur. Thus, one limitation of the printing speed is related to the speed at which the firing chamber is refilled.

A problem that sometimes appears in inkjet printheads is blockage that occurs in the ink supply channels or orifices of the printheads. Particulates can clog the channels leading to the ink firing chamber, which can lead to premature failure of the heater resistor, misdirection of the droplets, or a reduction in ink supply to the firing chamber caused by a significantly reduced ink droplet size. have. A single orifice that does not fire ink drops when instructed to fire ink drops leaves a missing portion in the printed text or forms a band of missing drops in the printed image. The end result is perceived as the poor quality of the print, i.e. a very undesirable characteristic for an inkjet printer. To address this undesirable result, use of spare or redundant ink ejection orifices in place of defective ink ejectors (see, eg, US Pat. Nos. 4,963,882 and 5,640,183) or multiple inlets to the ink firing chamber It is proposed to use.

Ink for inkjet printing is typically stored in a reservoir associated with a printhead device. Devices for storing ink, such as porous foam materials or sealed containers, are known to generate particulates that can occlude ink supply channels or jet orifices. Many of the microparticles were observed to be elongated fibrous microparticles, an undesirable product of the manufacturing process. Fibrous particulates are sometimes separated from the ink receiving device and printed by the ink, despite the specific cleaning treatment and ink filtering that occurs before the ink enters the printhead (as described in US Pat. Nos. 4,771,295 and 5,025,271). Is carried to the head. Filtering elongated particulates is described in US patent application Ser. No. 08 / 500,796, entitled "particle tolerant inkjet printhead architecture," filed July 11, 1995, under the name of Timothy Weber et al. It is mentioned, wherein the plurality of outer barrier islands prevent long particulates from reaching the ink supply channel or ink firing chamber. Ink filtering is also disclosed in US Pat. No. 5,463,413, wherein a plurality of pillars are arranged between the ink reservoir and the firing chamber, each pillar being coupled to the inlet of the firing chamber. The pillars are spaced at intervals below the minimum dimensions of the system and placed as close as possible to a common ink source to prevent particulates from entering the firing chamber. The minimum dimension of the system is likely to be the orifice aperture or the width of the passageway connecting the ink source to the firing chamber.

Because the sizes of the orifices, firing chambers and ink supply channels are reduced to provide improved printing properties, their small size causes particulates of the size that had passed through the ink supply channels and ejected from the orifices of conventional designs to block the printhead. can do. In designs applying orifices or ink supply channels having dimensions smaller than 20 μm, particulates and contaminants, such as skin cells, may be objects that can stagnate within the ink supply channels or orifices. Moreover, since particulates such as skin and other biological cells are not rigid, they can be deformed and passed through a filter with a pore size equal to the minimum dimension in the printhead. Conventional attempts to control and filter particulates are well suited for large particulates but do not solve the problem of small passages being blocked by smaller particulates.

An ink jet printer printhead that ejects ink from at least one firing chamber has a substrate having an ink ejector disposed thereon. The barrier layer is disposed on at least a portion of the substrate and has a thickness of the first dimension and has at least one ink supply channel for supplying ink from the ink source to the firing chamber. The ink supply channel has walls formed by elongated separation of the barrier layer, the substrate and the orifice plate. The long separation is defined by the width of the second dimension. The barrier layer has a plurality of islands, each island spaced from adjacent islands at intervals of a third dimension or less, disposed between the ink source and the at least one ink supply channel. The second dimension is at least the first dimension and the third dimension is smaller than the first dimension.

A typical inkjet cartridge is shown in FIG. 1, with the cartridge body 101 having a supply of ink therein, which sends ink to the printhead 103 through an ink conduit. Shown on the outer surface of the printhead are a plurality of orifices 105, which of the printer (not shown) are communicated to the printhead 103 via electrical connections 107 and associated conductive traces (not shown). Ink is selectively ejected through this orifice upon command. In one embodiment of the inkjet print cartridge, the printhead consists of a semiconductor substrate, film heater resistors disposed on or within the substrate, a photo definable barrier and adhesive layer, and a porosity. An orifice plate, which has a plurality of orifices 105 extending through it completely. Physical and electrical connections are formed on the flexible polymer tape 109 by beam lead bonding or similar semiconductor technology, where the flexible polymer tape is secured by an epoxy-like material for physical strength and fluid exclusion. The polymer tape 109 may be formed from Kapton®, marketed by 3M, or a similar material that may be photoablated or chemically etched to provide openings and other desired properties. Copper or other conductive traces may be attached or secured on one side of the tape such that the electrical interconnect 107 contacts the printer and connects to the substrate. The tape is typically bent and fixed around the edge of the print cartridge as shown.

A cross-sectional view of the printhead cut along the line A-A shown in FIG. 1 is shown in FIG. A portion of the body 201 of the cartridge 101 is shown, in which case the body of the cartridge is secured to the printhead by an adhesive with pressure. In a preferred embodiment, ink is supplied to the printhead by a common ink plenum 205 and also through the slot 206 in the printhead substrate 207. (As a variant, the ink may be supplied along the side of the substrate.) The heater resistors and associated orifices are typically arranged in two substantially parallel rows adjacent the inlet of the ink from the ink plenum. In most cases, the heater resistors and orifices are arranged staggered in their respective rows, and in a preferred embodiment the heater resistors are slots 206 of the substrate 207 as illustrated by the heater resistors 209, 211 of FIG. 2. Are located on both sides.

The orifice plate 203 is formed by electrodepositioning nickel on a mandrel having a peg and a barrier having a suitable dimension and an appropriate draft angle in a shape complementary to the desired shape in the orifice plate. By being formed, nickel of predetermined thickness adheres after the predetermined time passes. The resulting nickel film is removed after cooling and mechanically planarized for subsequent use. Nickel orifice plates are thinly coated with precious metals such as gold, palladium or rhodium to prevent corrosion. Following this fabrication, the orifice plate is attached to the semiconductor substrate 207 by the barrier layer 213. The orifice formed by electrodeposition on the mandrel extends through from the outer surface of the orifice plate 109 to the inner surface, which surface forms one of the walls of the ink firing chamber. Typically, the orifice is aligned directly above the heater resistor so that ink can be ejected from the orifice without the trajectory error introduced by the offset.

Substrate 207 and orifice plate 109 are attached to each other by barrier layer material 213. In a preferred embodiment, barrier layer material 213 is disposed on substrate 207 in a pattern form in which firing chambers 215 and 217 are formed in the area around the heater resistor. In addition, the barrier layer material is patterned such that ink is independently supplied to the firing chamber by one or more ink supply channels. Ink droplets 219 are selectively ejected by rapid heating of the heater resistor in accordance with the command of the printer. The substrate with the barrier layer attached to one surface is positioned relative to the orifice plate such that the orifice is exactly aligned with the heater resistor of the substrate.

In a preferred embodiment, the barrier layer 213 is a film negative photosensitive, polymerized by exposure to Parad®, Vacrel®, IJ5000®, or light or similar electromagnetic radiation. Polymeric photodefinable materials are used, such as other materials that are components, negative photosensitive, multi-component, polymeric dry films. This kind of material is available from DuPont, Wilmington, Delaware. The barrier layer is first applied as a continuous layer on the substrate 207 by applying adequate pressure and heat appropriate to the particular material selected. In general, the barrier layer film is sandwiched between mylar protective sheets. One sheet is removed to allow lamination of the barrier layer to the substrate. The other mylar sheet is left in place until the barrier layer is exposed. The photolithographic layer is exposed to ultraviolet light (preferably in the wavelength range of 440 nm to 340 nm) through a negative mask to polymerize the barrier layer material. The exposed barrier layer is subjected to chemical cleaning using a developer solvent of a 74 wt%: 26 wt% mixture of N-methyl-2-pyrrolidone and diethylene glycol. And the unexposed areas of the barrier layer are removed by chemical action. The remaining area of the barrier layer forms a wall of each ink firing chamber around each heater resistor. In addition, the remaining area of the barrier layer forms a wall of the ink supply channel from the ink firing chamber to an ink source (such as ink plenum 205 via a slot as shown in FIG. 2). This ink supply channel makes it possible to initially fill the ink firing chamber with ink and provide continuous refilling of the firing chamber after each ink ejection from the chamber. The speed at which ink enters and fills the ink firing chamber is an important factor in determining the highest speed a printer can print. In a preferred embodiment, two ink supply channels are formed in the barrier layer to connect the ink plenum and ink firing chamber, so that sufficient ink supply to the chamber is maintained and a significant portion of the energy generated during ink bubble vaporization Fast recharging can be realized without being lost from the supply channel.

Lamination of the orifice plate to the barrier layer is performed in a preferred embodiment by applying heating (about 200 ° C.) and pressure (50 psi to 250 psi) for a time up to 15 minutes. An adhesion promoter, such as disclosed in US Patent Application No. 08 / 742,118, filed by Garold Radke et al. On October 1, 1996, may be used to improve the adhesion between the orifice plate and the barrier layer. have. Final set up of the polymer and curing of the bond is achieved by heat soaking at about 220 ° C. for about 30 minutes.

One further feature is formed in the barrier layer of the preferred embodiment. At the inlet to each ink supply channel, a plurality of barrier layer islands 301 are arranged, as shown in a perspective view of the surface of the substrate (orifice plate removed) of FIG. 3. Each barrier island is made of a barrier material and extends the overall thickness of the barrier layer 213 from the substrate 207 to the orifice plate. In order to prevent delamination of the islands from the orifice plate or substrate, each barrier island provides an adhesive area of about 200 μm ² on each surface. The main purpose of such barrier islands is to prevent particulates and contaminants from the ink from reaching the ink supply channel and orifice of each firing chamber. Such filters require that, for proper function, the spacing S between each island (equivalent to the pore of the filter) is less than the channel width W of each firing chamber and less than the aperture of the orifice. Therefore, all contaminants that can stay in the ink supply channel or in the orifice are blocked from this limit area. As a result of multiple islands (and the spaces between them), the occlusion of any of the spaces between the islands does not seriously impede the flow of ink to each ink supply channel, and the likelihood of clogging of the ink firing chamber is significantly reduced. Is a filter. Experiments with various spacing dimensions (S = 10 [mu] m, 12 [mu] m and 14 [mu] m) have demonstrated that the performance of the printhead at high speed ink firing chamber refill is not affected by this range of dimensions.

In a preferred embodiment, the dimensions of many elements of the printhead are made significantly smaller than known designs in order to achieve high quality ink printing by using small ink droplets. The nominal weight of the ink drops is about 10 ng for injection from an orifice having an aperture of 18 μm (± 2 μm). In order to achieve an ink firing chamber refill rate that supports an operating frequency of 15 KHz, two offset ink supply channels 303, 305 are used to provide rich ink refill capability. Each ink supply channel has a channel width W of 17 μm (± 2 μm) and a channel length of about 30 μm. These dimensions of channels and orifices present a greater challenge to the filtering of contaminants than has been done previously in that particulates of human skin cell size may occlude the ink supply channels or orifices. Since particulates of this size contain some biological cells that are not rigid, the size of the filter pores should be smaller than the smallest operating dimension of the printhead to capture particulates that are likely to be occluded. Depending on the particular application, the smallest working dimension is an ink supply channel width W of 17 μm (± 2 μm) or an orifice aperture of about 18 μm. In a preferred embodiment, the spacing S between each island is 12 μm (± 0.5 μm). The thickness of the barrier layer is 14 μm (± 1.5 μm).

Negative photoresists are known primarily for limiting degradation due to swelling during the material photo development process. It is known that all shapes formed in the barrier layer, or the spaces between these shapes, should have dimensions that exceed the thickness dimension of the barrier layer. Referring to Weiss' "photoresist technology update" (Semiconductor International, April 1983), negative photoresist materials are limited to 1: 2 or 1: 3 layer thickness vs. geometric dimensions. However, positive type resists mention that a ratio of layer thickness to shape dimension can be 1: 1. An example of a cross sectional view of a desired ink supply channel is shown in FIG. 4A. The substrate 207 has a barrier layer 213 disposed on its surface. Orifice plate 109 is secured to barrier layer 213. The barrier layer has a channel 401 that is photodefined and developed into the barrier layer, so that the ink supply channel is formed by the narrowing of the substrate, barrier layer and orifice plate. If the width dimension of the channel is smaller than the thickness dimension of the barrier layer, an incomplete development occurs, and the bridge layer 403 of the barrier layer remains across the narrow channel as shown in FIG. 4B. This bridge closes the channel and reduces the flow of ink into the ink firing chamber.

It has been measured that depletion of dissolved oxygen during exposure limits the channel width that can form between large features. It is believed that oxygen diffusion is limited to a limited distance because of the predetermined barrier thickness, exposure amount, single exposure rate, temperature, and oxygen utilization at the barrier surface. When the barrier is thick enough to form channels within this distance, the oxygen diffusion proximity effect becomes more important than swelling in limiting the aspect ratio.

When a region of the barrier layer material is exposed to ionizing radiation, a chemical reaction is formed in the barrier film that forms free radicals, such as peroxy radicals. These free groups combine to form a crosslinking reaction, which imparts immunity to the developing solvent in the exposed areas to define the desired image. However, in a typical manufacturing environment, diatomic oxygen from air is in equilibrium with other components in the barrier layer film. Before the crosslinking reaction continues, the much more reactive oxygen molecules must first disappear. If the amount of radiation required for reaction with readily available oxygen is exceeded, additional radiation crosslinks the material.

Proximity effects causing "incomplete" (or "bridging") occur at the interface between the exposed and unexposed areas of the barrier, the exposed side depleting oxygen molecules and the unexposed side Still has equilibrium concentrations. Thus, because the barrier layer film is separated from the oxygen in the air by a mylar cover film, the instantaneous concentration gradients shift the oxygen molecules into the exposed areas from adjacent unexposed barriers to uniform the distribution of oxygen. . Oxygen migration from the unexposed channel lowers the amount of radiation required to expose the barrier, since fewer oxygen molecules are to be extinguished prior to the initiation of crosslinking, so that the masked channel is scattered from the unmasked region. Undesirably exposed. Therefore, in the inkjet printhead, when the barrier layer thickness is larger than the width of the feature to be developed, and the feature approaches the large volume of the barrier material, bridging of the feature is expected to occur. However, if the feature has a width dimension that is less than the barrier layer thickness but is at a distance from the large volume of the barrier material, it is less than the barrier thickness but greater than 0.6 times the barrier layer thickness at the exposure energy used to define the remaining pattern. No bridging occurs. The distance of the features must be separated from the volume of exposed material as large as two to five times the thickness of the barrier layer, depending on the actual size of the large volume of exposed material. Thus, in a preferred embodiment of the present invention, the islands 301 are spaced from the barrier layer of the nearest volume by a distance D of 10 μm (± 0.25 μm). It should be noted that the dimensions for the barrier layer features are given in the dimensions of the photo-resist mask. The spacing between the barrier layer walls and the spacing, such as barrier island spacing S and ink supply channel width W, are expected to be between 1 μm and 2 μm larger than the photoresist mask dimensions.

Thus, by installing an island of the barrier layer between the ink supply and the ink supply channel to the firing chamber and spaced apart by a distance less than the width or orifice aperture of the ink supply channel, the ink supply channel or orifice hole by the contaminants in the ink Occlusion will be reduced. If the spacing dimension between islands is smaller than the thickness of the barrier layer, bridging between islands is prevented by separating the islands from the rest of the barrier layer material.

The present invention can provide a printhead capable of reducing particulate blockage while maintaining a high speed ink filling by using a small sized particulate acceptable ink supply filter.

1 is a perspective view of a printhead for an inkjet printer,

2 is a cross-sectional view of a printhead that may be used in the inkjet print cartridge of FIG.

3 is a perspective view of a barrier layer and a substrate of a printhead in which the present invention may be used;

4A and 4B are cross-sectional views of ink supply channels showing the effect of barrier layer bridging.

Explanation of symbols for main parts of the drawings

101: cartridge body portion 103: printhead

203: orifice plate 207: substrate

213: barrier layer 301: island

303, 305: ink supply channel 403: bridge

Claims (6)

A printhead for an inkjet printer that ejects ink from at least one firing chamber, A substrate 207 having ink ejectors 209 and 211 disposed thereon; A barrier layer 213 disposed on at least a portion of the substrate, The barrier layer is The layer thickness of the first dimension, At least one ink supply channel 303, 305 for supplying ink from an ink source to the firing chamber, wherein the at least one ink supply channel is formed by an elongate separation of the barrier layer, the substrate and the orifice plate 203. At least one of the ink supply channels 303, 305 having a wall, the elongate separator being defined by a width W of a second dimension, A plurality of islands 301, each island of the plurality of islands spaced from adjacent islands by a third dimension S or less, disposed between the ink supply source and the at least one ink supply channel. Island 301, The second dimension is greater than the first dimension and the third dimension is less than the first dimension. Printhead. The method of claim 1, The orifice plate is disposed on the barrier layer and has orifices 215 and 217 therethrough, the orifice extending from the surface of the orifice plate closest to the barrier layer to the outer surface of the orifice plate and to the ink ejector. Relative to the ink ejector can be ejected by the ink ejector Printhead. The method of claim 2, The orifice plate further includes the orifice having a minimum aperture larger than the first dimension. Printhead. A method of manufacturing a printhead for an inkjet printer, which ejects ink from at least one firing chamber, Disposing a barrier layer 213 having a thickness of a first dimension on a portion of the substrate 207; Exposing a portion of the barrier layer to electromagnetic radiation, the portion having a wall of ink supply channels 303 and 305 and a plurality of islands 301 for supplying ink from an ink source to the firing chamber; The walls are spaced apart from each other by a second dimension (W), each of the plurality of islands being spaced apart from adjacent islands of the plurality of islands at intervals less than a third dimension (S), the ink source and the ink The exposing step, disposed between feed channels, wherein the second dimension is greater than the first dimension and the third dimension is less than the first dimension; Developing the barrier layer to remove a portion of the barrier layer that has not been exposed to electromagnetic radiation. Method of manufacturing a printhead. The method of claim 4, wherein Forming at least one orifice 215, 217 in orifice plate 203, the orifice extending from a first surface of the orifice plate to a second surface of the orifice plate and having a hole of a fourth dimension, The forming step, Disposing the orifice plate on the barrier layer, thereby allowing ink to be ejected by the ink ejector through the formed orifice; Method of manufacturing a printhead. The method of claim 5, Forming a fourth dimension of the hole larger than the first dimension; Method of manufacturing a printhead.